This is a proposal to serve as a statistical coordinating center for a multi-institutional randomized clinical trial of a low fat diet aimed at prolonging the disease-free survival and overall survival in stage II breast cancer patients. Three phases of the project include the protocol development, feasibility and implementation phases. In the protocol development the investigators from NCI, the clinical, the nutritional, and coordinating centers will develop a protocol for recruitment, treatment, dietary education), and data management and analyses plans. In the feasibility phase, a sample of 200 in the treatment group and 100 in the control group seem adequate for assessing compliance with the 20% low fat diet and any adverse effects of the treatment. With modification of existing clinical data collection and 24 hour - frequency nutritional dieting assessment instruments, the data collection and management system using the IBM XT as data entry work stations with a DEC 11 minicomputer for analysis should offer the speed and economy necessary for an effective feasibility study. Assuming that the feasibility phase indicates patients can comply with a low fat diet, and implementation phase will be initiated with a sample size of 2000. With only slight modifications to the instruments and protocol, the same data collection card arrangement systems could be enlarged to accommodate the additional work load.